Aluminum Foil: A Rising Star in Food Packaging

1911 was an important milestone in the history of world food packaging, because that year marked the debut of aluminum foil in the field of food packaging, thus beginning its glorious journey in food packaging. As a pioneer of aluminum foil packaging — a Swiss chocolate company — after more than 100 years of growth, has now become a household-name brand (Toblerone).

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Aluminum foil usually refers to aluminum material with a purity above 99.5% and a thickness below 0.2 mm, while the aluminum foil used in composite materials is even thinner. Of course, different countries have different requirements for the thickness and composition of aluminum foil. The question is, can aluminum foil as thin as a cicada's wing shoulder the heavy responsibility of food packaging? This has to start with the mission of food packaging and the properties of aluminum foil.

Although food packaging is generally inedible, it is an important part of a food product's commodity attributes. As far as the functions of food packaging are concerned, the most core one is the food-protection function. Food goes through a complex process from production to consumption, and may therefore be affected by biological, chemical, physical and other external factors in the environment. Food packaging should be able to maintain the stability of food quality and resist various adverse influences in the environment. At the same time, food packaging should also meet requirements in terms of aesthetics, convenience, environmental protection and low price.

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Let us now look at the properties of aluminum foil. First, aluminum foil has high mechanical strength and a certain impact- and puncture-resistance, so during storage and transport, foods packaged in aluminum foil are not easily damaged by squeezing, impact, vibration, temperature differences and other factors. Second, aluminum foil has high barrier properties, with very high resistance to sunlight, high temperature, moisture, oxygen, microorganisms and so on. These factors all promote food spoilage, and blocking them can extend the food's shelf life. Third, aluminum foil is easy to process and relatively low in cost, can meet the packaging needs of most foods, and has a beautiful silvery white color and a mysterious texture. Fourth, aluminum metal itself is a lightweight metal, and extremely thin aluminum foil even more so meets the basic requirements of lightweight packaging, which is of great significance for reducing transport costs. Fifth, aluminum foil is non-toxic and odorless and easy to recycle, meeting the requirements of green environmental protection and sustainable development.

However, in food-packaging practice, aluminum foil is generally rarely used alone, because aluminum foil itself has some shortcomings. For example, as aluminum foil is made even thinner, the number of pinholes increases, which affects its barrier performance. At the same time, thin, soft aluminum foil has limitations in tensile and shear resistance, and usually cannot be used for structural packaging. Fortunately, aluminum foil has very good secondary-processing performance: it can usually be composite-processed with other packaging materials to make composite packaging materials, thereby making up for the shortcomings of aluminum foil and improving the overall packaging performance of the composite packaging material.

We usually call a film made by combining two or more materials a composite film, and a packaging bag made from a composite film a composite-film bag. Generally, plastics, aluminum foil, paper and other materials can be made into composite films by methods such as bonding or heat sealing, thereby meeting the different packaging needs of a variety of foods. In modern packaging, almost all composite materials that require opacity and high barrier use aluminum foil as the barrier layer, because aluminum foil has a highly dense metal crystal structure and excellent barrier performance against any gas.

In flexible food packaging, there is a packaging material called "vacuum aluminized film". Is it the same as aluminum-foil composite packaging material? Although both contain a very thin aluminum layer, they are not the same material. Vacuum aluminized film is made by vacuum deposition, plating high-purity aluminum onto a plastic film under vacuum, whereas aluminum-foil composite material is made by combining aluminum foil with other materials through methods such as bonding or heat sealing.

Unlike aluminum-foil composite materials, the aluminized layer in aluminized film does not have the barrier function of aluminum foil; it is the substrate film itself that provides the barrier. Because the aluminized layer is much thinner than aluminum foil, aluminized film costs less than aluminum-foil composite material. Its application market is also very broad, but it is generally not used for vacuum packaging.

This article is excerpted from "Encyclopedic Knowledge" 2023.5A

——This article is reprinted from China Packaging Network (pack.cn), original link: http://news.pack.cn/show-379353.html